4.2.1. Bedrock Islands

The diversity of PLES in the bedrock islands dominated by hills is lower than that of the islands occupied by platforms. For example, the area of Hailing Island is similar to Xiachuan Island, but the PLES diversity of the former is higher because the platform occupies nearly 50% of the total area.

The hill and platform difference led to the ES and PS/LS dualistic pattern of the bedrock islands. Hills generally account for over 60% of the bedrock islands, and forest land in ES is mainly distributed in hilly areas, with an altitude of 16–517 m and steep slopes. Since hills are not developed on a large scale, a few primary and some secondary forests are preserved, with a large area of the artificial forest planted and the nature reserve established [54], leading to the idea that ES maintenance is better than that of other island types.

Generally, PS and LS are distributed on the platform at an altitude of 0–20 m. The platform area of the bedrock island is usually small; thus, the exploitation of PS and LS is limited. In PS, arable land irrigation mainly relies on reservoirs, resulting in more reservoirs reconstructed from bedrock islands than other islands under a water-scarce situation. In PS of the intertidal zone, since the shoal area is small, the aquaculture ponds cannot be built on a large scale. In LS, the natural environment of the bedrock islands is more suitable for harbor exploitation since they have a jagged coastline, deep near-shore water, and fewer barrier shoals. Thus, the number of harbor land in bedrock islands is more than that of other island types.
